Light-emitting module and integrated light-emitting module

ABSTRACT

A light-emitting module includes: a base body including electrical conductor wirings; a light-emitting element disposed on the base body and electrically connected to the electrical conductor wirings; a light reflection film disposed on an upper surface of the light-emitting element; and a half mirror disposed on a light extraction surface side of the light-emitting element and spaced apart from the light-emitting element. A spectral reflectance of the half mirror under perpendicular incidence at a wavelength longer than a peak emission wavelength of a light emitted from the light-emitting element is greater than a spectral reflectance of the half mirror under perpendicular incidence at the peak emission wavelength.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No.2017-204528, filed on Oct. 23, 2017, the contents of which are herebyincorporated by reference in their entirety.

BACKGROUND

The present disclosure relates to a light-emitting module and anintegrated light-emitting module.

In recent years, as a backlight for a display device such as a liquidcrystal display device, direct-type surface emission modules including asemiconductor light-emitting element have been proposed. In view offunctionality, design, etc., the thickness of such display devices isrequired to be reduced in some cases, and thus, the thickness of thebacklights for such display devices also needs to be reduced. Moreover,a reduction in the thickness of light-emitting modules for generalillumination applications may also be required, in view offunctionality, design, etc.

Reduction in the thickness of a light-emitting module for such usegenerally tends to cause unevenness in luminance at the emissionsurface. In particular, when a plurality of light-emitting elements arearranged in a one-dimensional or two-dimensional array, luminance willbe higher in a region directly above the light-emitting elements than intheir surrounding region. Therefore, for example, PCT Publication No.WO2012/099145 describes a technique in which a diffusive member isdisposed on a portion a surface of a resin body, which seals alight-emitting element and also functions as a lens, near a regiondirectly above the light-emitting element, to enhance the uniformity oflight emitted from the light source.

SUMMARY

The present disclosure provides a light-emitting module in whichunevenness in luminance is reduced.

In one embodiment, a light-emitting module comprises: a base bodyincluding electrical conductor wirings; a light-emitting elementdisposed on the base body to be electrically connected to the electricalconductor wirings; a light reflection film disposed on an upper surfaceof the light-emitting element; and a half mirror disposed on a lightextraction surface side of the light-emitting element and spaced apartfrom the light-emitting element, wherein a spectral reflectance of thehalf mirror under perpendicular incidence at a wavelength longer than apeak emission wavelength of a light emitted from the light-emittingelement is greater than a spectral reflectance of the half mirror underperpendicular incidence at the peak emission wavelength.

According to certain embodiments described in the present disclosure, alight-emitting module in which unevenness in luminance is reducedbetween a region above a light-emitting element and a region surroundingthe region above the light-emitting element.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross-sectional view showing an exemplary light-emittingmodule according to a first embodiment.

FIG. 1B is a cross-sectional enlarged view showing a portion of thelight-emitting module shown in FIG. 1A.

FIG. 2A is a diagram showing an example of spectral reflectioncharacteristics with respect to light perpendicularly incident on a halfmirror of the light-emitting module shown in FIGS. 1A and 1B.

FIG. 2B is a diagram showing spectral reflection characteristics withrespect to light obliquely incident, at 45°, on a half mirror having thespectral reflection characteristics shown in FIG. 2A.

FIG. 3A is a schematic diagram showing travel of light in an exemplarylight-emitting module in which a light reflection film 22 is provided onthe upper surface of the light-emitting element and a diffusion plate isdisposed above the upper surface of the light-emitting element. FIG. 3Bis a diagram illustrating emission by the light-emitting module shown inFIG. 3A.

FIG. 4 is a schematic diagram showing light emission from thelight-emitting element in the light-emitting module shown in FIGS. 1Aand 1B.

FIG. 5A is a cross-sectional view showing an exemplary light-emittingmodule according to a second embodiment.

FIG. 5B is a top view of an integrated light-emitting device havinglight-emitting modules as shown in FIG. 5A.

DETAILED DESCRIPTION

Hereinafter, embodiments of a light-emitting module and an integratedlight-emitting module according to the present disclosure will bedescribed with reference to the drawings. The light-emitting module andintegrated light-emitting module described below are exemplaryembodiments, and various modifications can be made to the embodimentsdescribed below. In the description below, terms indicating a directionor position (e.g., “above”, “below”, “right”, “left”, or other termssimilar to such terms) may be used. Such terms will be used for easierunderstanding of the relative directions and positions in the drawingsreferred to. The relative relationships of directions or positions inreferenced drawings, as indicated by terms such as “above”, “below”,“right”, “left”, etc., may be the same as those in drawings other thanthose of the present disclosure, in products, or the like, whilearrangements of components in the referenced drawings may not be thesame as arrangements of corresponding components in drawings other thanthose of the present disclosure, in products, or the like. The size, thepositional relationship or the like of structural elements in thedrawings may be exaggerated for easier understanding and may not reflectthe sizes, or the positional relationship between the structuralelements in the actual light-emitting module. In order to preventexcessive complexity, some elements may be omitted from illustration inschematic cross-sectional views or the like.

First Embodiment

FIG. 1A is a schematic diagram showing a partial cross-sectionalstructure of a light-emitting module 101 according to the presentembodiment. FIG. 1B is a schematic enlarged diagram showing a partialcross-sectional structure of the light-emitting module 101. Thelight-emitting module 101 includes a base body 10, a light-emittingelement(s) 21, a light reflection film 22, and a half mirror 51.Hereinafter, the respective component elements will be described indetail.

Base Body 10

The base body 10 has an upper surface and supports the light-emittingelement(s) 21. The base body 10 also supplies electric power to thelight-emitting element(s) 21. The base body 10 includes a substrate 11and electrical conductor wirings 12, for example. The base body 10 mayfurther include an insulating layer 13.

The substrate 11 may be made of, for example, a resin such as a phenolicresin, an epoxy resin, a polyimide resin, a BT resin, polyphthalamide(PPA), or polyethyleneterephthalate (PET), a ceramic, or the like. Amongthese, in view of cost reduction and ease of molding, an electricallyinsulating resin is preferably chosen. Alternatively, in order torealize a light-emitting module having good thermal resistance and lightresistance, a ceramic may be selected as a material of the substrate 11.Examples of such ceramics include, alumina, mullite, forsterite, glassceramics, nitride-based ceramics (e.g. AlN), and carbide-based ceramics(e.g. SiC). Among these, ceramics made of alumina, or ceramicscontaining alumina as a main component are preferable.

In the case in which a resin is used as a material of the substrate 11,an inorganic filler such as glass fibers, SiO₂, TiO₂, or Al₂O₃ may bemixed in the resin to improve the mechanical strength, reduce thecoefficient of thermal expansion, improve the light reflectance, etc.The substrate 11 may be a composite plate in which an insulating layeris formed on a metal plate.

The electrical conductor wiring 12 has a predetermined wiring pattern.The electrical conductor wiring 12 is electrically connected toelectrodes of the light-emitting element 21 to allow electric power tobe supplied from external components to the light-emitting element 21.The wiring pattern includes a positive wiring that is connected to apositive electrode of the light-emitting element 21 and a negativewiring that is connected to a negative electrode of the light-emittingelement 21. The electrical conductor wiring 12 is disposed at least onan upper surface of the base body 10 that serves as a surface on whichthe light-emitting element 21 is to be mounted. A material of theelectrical conductor wiring 12 may be appropriately selected fromelectrically conductive materials in accordance with a material of thesubstrate 11, a method of producing the substrate 11, and so on. Forexample, when a ceramic is used as a material of the substrate 11, amaterial of the electrical conductor wiring 12 is preferably ahigh-melting point material that can withstand the baking temperature ofthe ceramic sheet; for example, a metal having a high melting point suchas tungsten or molybdenum is preferably used. On the wiring pattern of ahigh-melting point metal, a layer of another metal material, e.g.,nickel, gold, or silver, may further be provided by plating, sputtering,vapor deposition, or the like.

In the case in which a resin is used as a material of the substrate 11,a material that is easy to process is preferably used as a material ofthe electrical conductor wiring 12. In the case in which a resin isinjection-molded to be used as a material of the substrate 11, amaterial that is easily subject to processing such as a punchingprocessing, an etching processing, a bending processing, or the like andhas a relatively large mechanical strength is preferably used as amaterial of the electrical conductor wiring 12. More specifically, theelectrical conductor wiring 12 is preferably a metal layer, a leadframe, etc., made of a metal such as copper, aluminum, gold, silver,tungsten, iron, nickel, an iron-nickel alloy, phosphor bronze,iron-containing copper, molybdenum, or the like. Moreover, on a surfaceof a wiring pattern of such a metal, the electrical conductor wiring 12may further include an additional layer of metal material. Anappropriate material may be used for the additional layer, and forexample, a layer made of only silver, or a layer made of an alloycontaining silver and copper, gold, aluminum, rhodium, or the like maybe used. Alternatively, a multilayer structure containing silver and/orsuch an alloy may be used for the additional layer. The additional layerof metal material may be formed by plating, sputtering, vapordeposition, or the like.

Insulating Layer 13

The base body 10 may include an insulating layer 13. In the base body10, the insulating layer 13 is disposed on the substrate 11 to cover aportion of the electrical conductor wiring 12 to which thelight-emitting element 21 and the like are connected. In other words,the insulating layer 13 is electrically insulating, and covers at leasta portion of the electrical conductor wiring 12. The insulating layer 13preferably has a light-reflecting property. With the insulating layer 13having a light-reflecting property, light that is emitted from thelight-emitting element 21 toward the base body 10 is reflected by theinsulating layer 13, so that the light extraction efficiency can beimproved. Moreover, with the insulating layer 13 having alight-reflecting property, among the light emitted from a light sourceand is incident on a light-transmissive layered structure including adiffusion plate, a wavelength conversion member, or the like, forexample, a light reflected at the light-transmissive layered structureto return toward the base body 10 is also reflected by the insulatinglayer 13, so that the light extraction efficiency can be improved. Suchlight reflected at the base body is also transmitted through thelight-transmissive layered structure, so that unevenness in luminancecan be further reduced.

Any appropriate material that absorbs little light emitted from thelight-emitting element 21 and is electrically insulating may be used forthe insulating layer 13. For example, resin materials such as epoxies,silicones, modified silicones, urethane resins, oxatane resins,acrylics, polycarbonates, or polyimides may be used. In the case inwhich light-reflecting property is imparted to the insulating layer 13,in the insulating layer 13, a resin material as described above maycontain a white-based color filler that is the same as that to be addedto an underfill material described below. The white-based color fillerwill be described in detail below.

Light-Emitting Element 21

The light-emitting module 101 includes one or more light-emittingelements 21 that are disposed on the base body 10. When thelight-emitting module 101 includes a plurality of light-emittingelements 21, the light-emitting elements 21 are arranged in aone-dimensional or two-dimensional array on the base body 10. For thelight-emitting element(s) 21 disposed on the base body 10, various kindsof light-emitting element(s) can be used. Each light-emitting element 21is a light-emitting diode in the present embodiment. The wavelength ofthe light to be emitted from the light-emitting element 21 can beappropriately selected. For example, for a blue or green light-emittingelement, a light-emitting element using a semiconductor such as anitride-based semiconductor (e.g., In_(x)Al_(y)Ga_(1-x-y)N, 0≤X, 0≤Y,X+Y≤1), ZnSe, or GaP can be used. For a red light-emitting element, alight-emitting element using a semiconductor such as GaAlAs or AlInGaPcan be used. A semiconductor light-emitting element made of a materialother than these materials may alternatively be used. The number oflight-emitting elements to be used and their composition, emissioncolor, size, etc., may be appropriately selected in accordance with thepurpose.

In the case in which light emitted from the light-emitting element 21 issubjected to wavelength conversion using a wavelength conversion member,a nitride semiconductor (In_(x)Al_(y)Ga_(1-x-y)N, 0≤X, 0≤Y, X+Y≤1) thatemits light of a shorter wavelength that can efficiently excite awavelength conversion material contained in the wavelength conversionmember is preferably used for the light-emitting element 21. Variousemission wavelengths can be selected based on a material and a ratio ofmixed crystals of the semiconductor layera. The light-emitting element21 may have a positive electrode and a negative electrode at the samesurface or different surfaces of the light-emitting element 21.

Each light-emitting element 21 includes, for example, a growth substrateand semiconductor layers layered on the growth substrate. Thesemiconductor layers include an n-semiconductor layer, a p-semiconductorlayer, and an active layer disposed therebetween. The negative electrodeand the positive electrode are electrically connected to then-semiconductor layer and the p-semiconductor layer, respectively. Forthe growth substrate, for example, a light-transmissive sapphiresubstrate or the like can be used.

The n-side electrode and the p-side electrode of the light-emittingelement 21 are flip-chip mounted on the base body 10, via connectionmembers 23. More specifically, by the connection members 23, the p-sideelectrode and the n-side electrode of the light-emitting element 21 areelectrically connected to the positive wiring and the negative wiring,respectively, that are included in the electrical conductor wiring 12 ofthe base body 10. A surface of the light-emitting element 21 opposite toa surface thereof where the n-side electrode and the p-side electrodeare disposed, i.e., an upper surface 21 a, which is a principal surfaceof a light-transmissive sapphire substrate, serves as a light exitingsurface. In the present embodiment, in order to reduce the luminancedirectly above the light-emitting element 21, the light reflection film22 is disposed on the upper surface 21 a of the light-emitting element21. With this arrangement, a lateral surface 21 c of the light-emittingelement 21 serves as the primary light extraction surface.

Connection Member 23

As described above, by the connection members 23, the p-side electrodeand n-side electrode are connected to the positive wiring and negativewiring, respectively, of the electrical conductor wirings. Theconnection members 23 contain an electrically conductive material.Examples of a material of the connection members 23 include anAu-containing alloy, an Ag-containing alloy, a Pd-containing alloy, anIn-containing alloy, a Pb—Pd-containing alloy, an Au—Ga-containingalloy, an Au—Sn-containing alloy, an Sn-containing alloy, anSn—Cu-containing alloy, an Sn—Cu—Ag-containing alloy, anAu—Ge-containing alloy, an Au—Si-containing alloy, an Al-containingalloy, a Cu—In-containing alloy, a mixture of a metal and flux, or thelike.

The connection members 23 can be used in a liquid form, paste form, orsolid form (e.g., in a form of sheets, blocks, powder, or wires). A formof the connection members 23 may be appropriately selected in accordancewith the composition, shape of a base body, or the like. Each suchconnection member 23 may be made of a single member, or a combination ofseveral types of members.

Underfill Member 24

An underfill member 24 may be provided between the light-emittingelement 21 and the base body 10. The underfill member 24 preferablycontains a filler, for the purposes of allowing light emitted from thelight-emitting element 21 to be efficiently reflected, having acoefficient of thermal expansion closer to that of the light-emittingelement 21, or the like. In the present embodiment, because the lateralsurface 21 c of the light-emitting element 21 also serves as a lightextraction surface, the underfill member 24 preferably does not coverthe lateral face 21 c, as shown in FIGS. 1A and 1B.

As a base material of the underfill member 24, the underfill member 24contains a material that absorbs little light from the light-emittingelement. For example, epoxies, silicones, modified silicones, urethaneresins, oxatane resins, acrylics, polycarbonates, polyimides, and thelike can be used as the base material of the underfill member 24.

For the filler of the underfill member 24, using a white-type filler mayallow light to be reflected more easily, thus improving the lightextraction efficiency. An inorganic compound is preferably used for thefiller. As used herein, the expression “white” includes the case inwhich the filler itself is transparent but appears to be white whenscattering occurs due to difference between a refractive index of thefiller and that of a material surrounding the filler.

The reflectance of the filler is preferably 50% or more, and morepreferably 70% or more, with respect to a light of the emissionwavelength of the light-emitting element 21. This allows the lightextraction efficiency of the light-emitting module 101 to be improved.The particle size of the filler is preferably in a range of 1 nm to 10μm. With the filler having a particle size in this range, the underfillmaterial will have a good resin fluidity, so that the material servingas the underfill member 24 can be introduced even through a narrowspace. The particle size of the filler is preferably in a range of 100nm to 5 μm, and more preferably in a range of 200 nm to 2 μm. The fillermay have a spherical shape or a flake shape.

Specific examples of the filler material include: oxides such as SiO₂,Al₂O₃, Al(OH)₃, MgCO₃, TiO₂, ZrO₂, ZnO, Nb₂O₅, MgO, Mg(OH)₂, SrO, In₂O₃,TaO₂, HfO, SeO, and Y₂O₃; nitrides such as SiN, AlN, and AlON; andfluorides such as MgF₂. These may be used singly, or they may be used ina mixture.

Light Reflection Film 22

The light reflection film 22 reflects a portion of an incident light,and transmits another portion of the incident light. The lightreflection film 22 is disposed on the upper surface 21 a of thelight-emitting element 21. With this structure, a portion of lightemitted from the upper surface 21 a of the light-emitting element 21 isreflected by the light reflection film 22, returns to the light-emittingelement 21, and is emitted through the lateral surface 21 c of thelight-emitting element 21. As a result, the amount of light emitted fromthe upper surface 21 a of the light-emitting element 21 can be reduced;luminance above the light-emitting element 21 can be reduced; andunevenness in luminance can be reduced when the light-emitting module101 is used to configure a backlight or the like.

The reflectance of the light reflection film 22 is preferably in a rangeof 20% to 80% with respect to the peak emission wavelength of thelight-emitting element 21. With the reflectance less than 20%, theamount of light emitted from the upper surface 21 a is not sufficientlydecreased, so that unevenness in luminance is not sufficiently reduced.With the reflectance greater than 80%, the amount of light that isemitted from the upper surface 21 a is excessively decreased, so that,even with the use of the half mirror 51 to be described below, theluminance in the region above the upper surface 21 a is lower than thatin the surrounding region, which may lead to difficulty in reduction inunevenness in luminance.

It is preferable that the light reflection film 22 allow 30% or more ofthe total amount of light emitted from the light-emitting element 21 tobe emitted at an angle of elevation less than 20° with respect to theupper surface of the base body 10. The reflectance of the lightreflection film 22 can be adjusted so that light will be emitted fromthe light-emitting element 21 with such light-distributioncharacteristics.

The light reflection film 22 can be a metal film, a multilayereddielectric film, or the like. It is preferable that a material that doesnot easily absorb light emitted from the light-emitting element 21 beused.

Sealing Member 30

The light-emitting module 101 may include a sealing member 30. Thesealing member 30 protects the light-emitting element(s) 21 from theexternal environment, and optically controls the light-distributioncharacteristics of the light to be emitted from the light-emittingelement(s) 21. More specifically, refraction of light at the outersurface of the sealing member 30 allows for adjusting the direction oflight emission. The sealing member 30 is disposed on the base body 10 tocover the light-emitting element(s) 21.

The surface of the sealing member 30 is a convex curved surface. In topview, the sealing member 30 preferably has a circular or elliptic outershape. In the sealing member 30, a ratio H/W between the height H alongthe optical axis L and the width W in top view is preferably smallerthan 0.5. More preferably, H/W is 0.3 or smaller. The height H of thesealing member 30 is defined by an interval between a mounting surfaceof the base body 10 and the highest portion of the sealing member 30, astaken along the optical axis L. The width W is based on the shape of thebottom surface of the sealing member 30. When the bottom surface of thesealing member 30 has a circular shape, the width W refers to thediameter of the circle. When the bottom surface of the sealing member 30has another shape, the width W refers to the minimum width of the bottomface. For example, when the outer shape of the bottom surface in topview is an ellipse, the bottom surface has both a major axis and a minoraxis, and the minor axis refers to the width W of the bottom surface.With the sealing member 30 having this shape, light emitted from thelight-emitting element 21 can be refracted at the interface between thesealing member 30 and an air, so that a wider light distribution can beachieved.

Example of a material of the sealing member 30 include alight-transmitting resin such as an epoxy resin, a silicone resin or amixed resin thereof and glass. Among these, in view of light resistanceand ease of molding, a silicone resin is preferably selected.

The sealing member 30 may contain a wavelength conversion material and adiffusion agent for diffusing the light emitted from the light-emittingelement 21. Moreover, the sealing member 30 may contain a coloring agentcorresponding to the emission color of the light-emitting element. Inthe sealing member 30, such a wavelength conversion material, adiffusion material, a coloring agent, etc., are preferably contained atamounts that allow light distribution to be controlled on the basis ofthe outer shape of the sealing member 30. In order to reduce influenceon the light-distribution characteristics, the particle size of anymaterial contained in the sealing member 30 is preferably 0.2 μm orless. In the present specification, the expression “particle size”refers to an average particle size (i.e., median diameter), and thevalue of an average particle size can be measured by laserdiffractometry.

Half Mirror 51

The half mirror 51, which reflects a portion of an incident light andtransmits another portion of the incident light, is disposed above theupper surface 21 a of the light-emitting element(s) 21. It is preferablethat the half mirror 51 be sufficiently large relative to thelight-emitting element 21 so that even light emitted from thelight-emitting element 21 at a small angle of elevation can be incidenton the half mirror 51. In the case in which a plurality oflight-emitting elements 21 are arranged on the base body 10, the halfmirror 51 has a sufficient size for covering over the upper surfaces 21a of the plurality of light-emitting elements 21. The half mirror 51 maybe supported by a housing that holds the light-emitting module 101, forexample.

In the case in which the light-emitting module 101 further includes awavelength conversion member 52, a light-transmissive layer 53, whichwill be described below, or the like, the half mirror 51, the wavelengthconversion member 52, the light-transmissive layer 53 and the like arestacked so as to constitute a light-transmissive layered structure 50,and the light-transmissive layered structure 50 may be supported by ahousing that holds the light-emitting module 101, etc. In this case, inthe light-transmissive layered structure 50, the half mirror 51 ispreferably located closest to the light-emitting element 21.

In order to reduce unevenness in luminance between the region above thelight-emitting element 21 and the region surrounding the region abovethe light-emitting element 21, the half mirror 51 has spectralreflectance characteristics including at least two regions withdifferent spectral reflectances in the reflection wavelength band. FIG.2A shows a schematic example of spectral reflectance characteristics ofthe half mirror 51 with respect to perpendicular incident light. Aschematic example of an emission spectrum of light emitted from thelight-emitting element 21 is also shown. As shown in FIG. 2A, the halfmirror 51 has reflection characteristics in which a spectral reflectanceof the half mirror 51 under perpendicular incidence at the longerwavelength side B_(L) than a peak emission wavelength of a light emittedfrom the light-emitting element 21 is greater than a spectralreflectance of the half mirror 51 under perpendicular incidence at thepeak emission wavelength.

The half mirror 51 preferably has spectral reflectance characteristicsin which the spectral reflectance as described above in a region R_(L),which is located 50 nm from the peak emission wavelength region R_(E) onthe longer wavelength side, is 10% or more greater than the spectralreflectance in the peak emission wavelength region R_(E) of thelight-emitting element 21. As used herein, the expression “spectralreflectance” refers to a value with respect to perpendicular incidentlight. The “emission peak wavelength region R_(E) ^(”) is a wavelengthregion with a predetermined width including a peak emission wavelength 2of the light-emitting element 21 as the center thereof. For example, thepeak emission wavelength region R_(E) may be a wavelength region in arange of λ_(E1) and λ_(E2) (λ_(E1)<λ_(E2)). The bandwidth of the peakemission wavelength region R_(E) is determined based on thecharacteristics of light that is emitted from the light-emitting element21. For example, in the case in which the light-emitting element 21 isan LED that emits blue light, the bandwidth of the emission peakwavelength region R_(E) may be λ_(p)±20 nm.

The “region R_(L)” is a region including a region where the maximumwavelength and the minimum wavelength are are located 50 nm longerwavelength side of the maximum wavelength and the minimum wavelength,respectively, of the emission peak wavelength region R_(E). Morespecifically, the region R_(L) is a wavelength region in a range of(λ_(E1)+50) nm and (λ_(E2)+50) nm. The expression “the spectralreflectance in the region R_(L) is 10% or more greater than the spectralreflectance in the emission peak wavelength region R_(E) of thelight-emitting element 21” refers to that the spectral reflectance atany wavelength in the region R_(L) is 10% or more greater than thelargest spectral reflectance in the emission peak wavelength regionR_(E). The spectral reflectance in the emission peak wavelength regionR_(E) is in a range of 30% to 65%. Therefore, the spectral reflectancein the region R_(L) is in a range of 40% to 75%. The emission peakwavelength region R_(E) and the region R_(L) do not overlap each other.For example, the spectral reflectance of the half mirror 51 may beconstant within each of a longer wavelength region, which includes theregion R_(L), and a shorter wavelength region, which includes theemission peak wavelength region R_(E).

A reflection wavelength band B under perpendicular incidence refers to aregion including the peak emission wavelength region R_(E) and regionR_(L), and having the spectral reflectance of 40% or more and awavelength range of 400 nm to 800 nm. The reflection wavelength band Bof the half mirror 51 includes the peak emission wavelength of thelight-emitting element 21, and the longer wavelength side width B_(L)with respect to the peak emission wavelength is wider than the shorterwavelength side width B_(S).

The half mirror 51 is light-transmissive, and includes a multilayereddielectric film structure in which a plurality of insulating layershaving different refractive indices is layered. Examples of specificmaterials of the insulating layers include a material that absorbslittle light in the wavelength region of emission from thelight-emitting element 21, such as a metal oxide film, a metal nitridefilm, a metal fluoride film, and an organic material. Moreover, anorganic layer of a silicone resin, a fluororesin, or the like may beused for the insulating layers.

The spectral reflectance characteristics of the half mirror 51, morespecifically, the positions of the peak emission wavelength region R_(E)and region R_(L), spectral reflectance, etc., may be appropriately setthrough adjustments of the thicknesses of the insulating layers,refractive indices of the insulating layers, or the number of insulatinglayers of multilayered dielectric film, or the like. The spectralreflectances, etc., of the emission peak wavelength region R_(E) andregion R_(L) can be separately designed.

Wavelength Conversion Member 52

In the case in which the sealing member 30 does not contain a wavelengthconversion material, the light-emitting module 101 may further include awavelength conversion member 52. The wavelength conversion member 52 isspaced apart from the light-emitting element 21, and is disposed on alight extraction surface side of the light-emitting element. Thewavelength conversion member 52 is preferably spaced apart also from thesealing member 30. The wavelength conversion member 52 absorbs a portionof light emitted from the light-emitting module 101, and emit light of awavelength different from the wavelength of light emitted from thelight-emitting module 101. With the wavelength conversion member 52apart from the light-emitting element 21 of the light-emitting module101, even light conversion substances of small heat resistance or lightresistance, which would be difficult to use near the light-emittingelement 21, can be used. Accordingly, the performance of thelight-emitting module 101 as a backlight can be improved. The wavelengthconversion member 52 is in a form of a sheet or a layer, and contains awavelength converting substance.

Examples of the wavelength converting substance include yttrium aluminumgarnet (YAG)-based fluorescent materials activated by cerium, lutetiumaluminum garnet (LAG) activated by cerium, nitrogen-containing calciumaluminosilicate (CaO—Al₂O₃—SiO₂)-based fluorescent materials activatedby europium and/or chromium, silicate ((Sr,Ba)₂SiO₄)-based fluorescentmaterials activated by europium, βSiAlON fluorescent materials,nitride-based fluorescent materials such as CASN-based or SCASN-basedfluorescent materials, KSF-based fluorescent materials (K₂ SiF₆: Mn),and sulfide-based fluorescent materials. A fluorescent material otherthan these fluorescent materials that exhibits similar performance,action, and effects may also be used.

The wavelength conversion member 52 may contain, for example, alight-emitting substance such as so-called nanocrystals or quantum dots.For these materials, semiconductor materials can be used. Examplesthereof include II-VI group, III-V group, and IV-VI groupsemiconductors, and more specifically, nano-sized high-dispersionparticles of CdSe, core shell-type CdS_(x)Se_(1-x)/ZnS, GaP, or thelike.

Light-Transmissive Layer 53

The light-emitting module 101 may further include one or morelight-transmissive layers 53. Each light-transmissive layer 53 may be adiffusion plate, a prism sheet, a reflective polarization sheet, or thelike. The diffusion plate diffuses and transmits incident light. Thediffusion plate may be made of a material with a small light absorptionwith respect to visible light, e.g., a polycarbonate resin, apolystyrene resin, an acrylic resin, or a polyethylene resin. Thediffusion plate may have a structure for diffusing light providedthereon, such as irregularities on a surface of the diffusion plate, ordispersion of a material having a refractive index different from thediffusion plate in the diffusion plate. For the diffusion plate, adiffusion plate commercially available under names such as light adiffusing sheet, a diffuser film, etc., may be used.

With an increase in a perpendicular component of the light emitted fromthe light-transmissive layered structure 50, the prism sheet enhancesthe luminance when the emission plane of the light-emitting module 101is viewed from the front side.

A reflective polarization sheet is also called a luminance enhancementfilm. Of the light emitted from the light-emitting element 21, thereflective polarization sheet may transmit P-polarized light and reflectS-polarized light toward the light-emitting element 21, for example. TheS-polarized light having been reflected by the reflective polarizationsheet is reflected by the half mirror 51, the wavelength conversionmember 52, and the upper surface of the base body 10, and converted intoP-polarized light. The converted P-polarized light is transmittedthrough the reflective polarization sheet and emitted toward theoutside. In this manner, the proportion of the P-polarized lightcomponent in the light emitted from the light-emitting module 101 can beincreased.

Light-Emission and Effect of Light-Emitting Module 101

In the light-emitting module 101, the light reflection film 22 isdisposed on the upper surface 21 a of the light-emitting element 21.With this structure, a portion of light emitted from the upper surface21 a of the light-emitting element 21 is reflected at the lightreflection film 22, returns to the light-emitting element 21, and isemitted through the lateral surface 21 c of the light-emitting element21. Accordingly, the amount of light emitted through the upper surfaceof the light-emitting element 21 can be reduced, which allows forreducing the luminance in a region above the light-emitting element 21,so that unevenness in luminance can be reduced when a backlight or thelike is configured using the light-emitting module 101.

According to the study of the inventors, when a multilayered dielectricfilm is disposed on the upper surface of the light-emitting element anda diffusion plate or the like is disposed on the light-emitting side ofthe light-emitting module to form a backlight, a reduction in thedistance between the diffusion plate and the light-emitting elementallows the luminance near a region above the light-emitting element tobe smaller than that of a region surrounding the region above thelight-emitting element. FIG. 3A shows a schematic cross-sectional viewof an exemplary light-emitting module 100 in which a light reflectionfilm 22 is disposed on the upper surface of the light-emitting element21 and a diffusion plate 61 is disposed above the upper surface 21 a.

FIG. 3B shows an example of observed light emission by a prototypedlight-emitting module 100, when viewed from its upper surface side.

With reduction in the interval D between the diffusion plate 61 and thelight-emitting element 21, in the diffusion plate 61, a light that hasperpendicularly emitted from of the upper surface 21 a of thelight-emitting element 21 and has been transmitted through the lightreflection film 22 is incident on a region 61 a above the light-emittingelement. On the other hand, light obliquely emitted from the uppersurface 21 a of the light-emitting element and transmitted through thelight reflection film 22, and light reflected at the light reflectionfilm 22 and then reflected at an inner portion of the light-emittingelement 21 to be emitted from the upper surface 21 a of thelight-emitting element 21 and the lateral surface 21 c are incident on aregion 61 b, which surrounds the region 61 a. Thus, as shown in FIG. 3B,the luminance in the region above the light-emitting element 21 is lowerthan the luminance in the region surrounding the region above thelight-emitting element 21, which may lead to an unevenness in luminance.

In the light-emitting module 101 according to the present disclosure, anincident angle dependence of the spectral reflection characteristics ofthe half mirror 51 is used to reduce unevenness in luminance asdescribed above. Generally, when a half mirror is made of a multilayereddielectric film, spectral reflection characteristics of a lightperpendicularly incident on the half mirror 51 and that of a lightobliquely incident on the half mirror 51 are different from each other.The optical path length of a light obliquely incident on the half mirroris longer than the optical path length of a light perpendicularlyincident on the half mirror, which allows the reflection wavelength bandto be shifted toward the shorter wavelength side. This is also called a“blue shift”. FIG. 2B shows spectral reflectance characteristics withrespect to light incident in a direction of 45° with respect to adirection perpendicular to the half mirror 51, where the half mirror 51has the spectral reflectance characteristics show in FIG. 2A.

The light-emitting element 21 has a peak emission wavelength of about450 nm, and a peak emission wavelength region R_(E) is a range of 430 nmto 470 nm. The region R_(L) is a range of 480 nm to 520 nm. The spectralreflectance in the peak emission wavelength region R_(E) is about 42%,and the spectral reflectance in the region R_(L) is about 60%. That is,while light perpendicularly incident on the half mirror 51 is reflectedwith a spectral reflectance of about 42%, light obliquely incident onthe half mirror 51 is reflected with a spectral reflectance of about 60%at the maximum.

According a detailed study, in the case of a light-emitting element 21for emitting, e.g. blue light, the amount of shift of 50 nm allows forincreasing luminance in the region above the light-emitting element 21while reducing luminance in the region surrounding the region above thelight-emitting element 21, so that unevenness in luminance can beefficiently reduced.

FIG. 4 schematically shows travel of light emitted from thelight-emitting element 21 in the light-emitting module 101. In the casein which the distance D between the upper surface 21 a of thelight-emitting element 21 and the half mirror 51 is small, as has beendescribed with reference to FIG. 3A and FIG. 3B, a greater amount oflight is incident on the region 51 a above the light-emitting element 21than on the region 51 b surrounding the region 51 a, in the half mirror51.

Light incident on the region 51 a of the half mirror 51 contains manycomponents perpendicular to the half mirror 51. Thus, light incident onthe region 51 a is reflected at the half mirror 51 with a reflectance ofabout 42%; in other words, about 58% of light incident on the region 51a is transmitted through the half mirror 51. On the other hand, lightincident on the region 51 b contains many components oblique to the halfmirror 51. Thus, light incident on the region 51 b is reflected at thehalf mirror 51 with a reflectance of 60% at the maximum; i.e., about 40%of light incident on the region 51 b is transmitted through the halfmirror 51. This allows luminance in the region 51 a of the half mirror51 to be relatively increased, and luminance in the region 51 b to bereduced, so that unevenness in luminance on the emission plane of thelight-emitting module 101 can be reduced.

Thus, in the light-emitting module 101 according to the presentdisclosure, with the light reflection film 22 disposed on the uppersurface 21 a of the light-emitting element 21, light emitted from thelight-emitting element 21 can be widely distributed. With this widedistribution, the luminance in the region directly above thelight-emitting element 21 can be lower than the luminance surroundingthe region directly above the light-emitting element 21, and thus thehalf mirror 51 having the characteristics as described above is employedso that light from the light-emitting element 21 will go outtherethrough. This allows for reducing unevenness in luminance even whenthe distance D of the light-emitting module 101 is reduced, and thus athin-type backlight can be realized.

Further, with the sealing member 30 having an outer shape with a convexcurved surface, and with the ratio H/W of height to width smaller than0.5, light emitted from the light-emitting element 21 can be even widelydistributed. For example, with the ratio H/W of the height H to thewidth W of the sealing member 30 to be 0.3 or smaller, 40% or more ofthe total amount of light emitted from the light-emitting module 101 canbe emitted at an angle of elevation that is less than 20° with respectto the upper surface of the base body 10. With the light reflection film22 and the outer shape of the sealing member 30, it is possible toobtain desired light-distribution characteristics without using asecondary lens. That is, the light reflection film 22 allows forreducing luminance in a region above the light-emitting element 21, andthus the sealing member 30 mainly has the function of broadeningdistribution of the light emitted from the light-emitting element 21.This allows for greatly reducing the size the sealing member 30 having alens function. Thus, with the light-emitting module 101, a thinbacklight module (light-emitting module) in which unevenness inluminance is reduced can be realized.

Second Embodiment

FIG. 5A is a schematic diagram showing a cross-sectional structure of anintegrated light-emitting module 102 according to the presentembodiment. The integrated light-emitting module 102 includes alight-transmissive layered structure 50 and an integrated light-emittingdevice 103. FIG. 5B is a top view of the integrated light-emittingdevice 103.

The integrated light-emitting device 103 includes a base body 10, aplurality of light-emitting elements 21 arranged on the base body 10,and a light reflection film 22 disposed on an upper surface of eachlight-emitting element 21. The structures of the base body 10, thelight-emitting element 21, and the light reflection film 22, and therelationship between these components are as have been described in thefirst embodiment.

The plurality of light-emitting elements 21 are arranged in aone-dimensional or two-dimensional array on the upper surface of thebase body 10. In the present embodiment, the plurality of light-emittingelements 21 are arranged in a two-dimensional array along two orthogonaldirections, i.e., the x direction and the y direction, where anarrangement interval P_(x) along the x direction and an arrangementinterval P_(y) along the y direction are the same. However, thearrangement directions are not limited to these. The intervals along thex direction and the y direction may be different, and the twoarrangement directions may not be perpendicular to each other. Moreover,the arrangement intervals do not need to be regular intervals, butrather may be irregular intervals. For example, the light-emittingelements 21 may be arranged such that their interval increases from thecenter of the base body 10 toward the periphery of the base body 10.

The integrated light-emitting device 103 includes a plurality oflight-reflecting members 15 located between light-emitting elements 21.Each light-reflecting member 15 has wall portions 15 ax and 15 ay andbottom portions 15 b. As shown in FIG. 5B, each of the wall portions 15ay extending along the y direction is located between two adjacentlight-emitting elements 21 along the x direction, and each of the wallportions 15 ax extending along the x direction is located between twoadjacent light-emitting elements 21 along the y direction. Thus, eachlight-emitting element 21 is surrounded by two wall portions 15 axextending along the x direction and two wall portions 15 ay extendingalong the y direction. Each bottom portion 15 b is located at a region15 r surrounded by the two wall portions 15 ax and the two wall portions15 ay. In the present embodiment, with the arrangement intervals of thelight-emitting elements 21 along the x direction and the y directionthat are the same, the outer shape of the bottom portion 15 b is asquare.

Each of the bottom portions 15 b has a through-hole 15 e at the centralpart thereof, and the bottom portions 15 b are located on the insulatinglayer 13 so that a light-emitting element 21 is disposed in thethrough-hole 15 e in a plan view. Each of the through-holes 15 e canhave any appropriate shape and size that allow a respective one of thelight-emitting elements 21 to be disposed in the through-hole. In orderto allow light emitted from each of the light-emitting elements 21 to bealso reflected by a respective one of the bottom portions 15 b, theouter edge of a respective one of the through-holes 15 e is preferablylocated near the light-emitting element 21. That is, in a top view, theinterval between the through-hole 15 e and the light-emitting element 21is preferably narrow.

As shown in FIG. 5B, in a yz cross section, each wall portion 15 axincludes a pair of slopes 15 s extending along the x direction. Eachslope 15 s has two edges extending along the x direction such that thepair of slopes 15 s are connected together at one of the two edgesthereof to constitute an apex 15 c. The other edge of each pair ofslopes 15 s is connected to a respective one of the bottom portions 15 bof two adjacent regions 15 r. Similarly, each wall portion 15 ayextending along the y direction includes a pair of slopes 15 t extendingalong the y direction. Each slope 15 t has two edges extending along they direction such that the pair of slopes 15 t are connected together atone of the two edges to constitute an apex 15 c. The other edge of eachpair of slopes 15 t is connected to a respective one of the bottomportions 15 b of two adjacent regions 15 r.

Each bottom portion 15 b, two corresponding wall portions 15 ax, and twocorresponding wall portions 15 ay define a light-emission space 17having an opening. FIG. 5B illustrate light-emission spaces 17 arrangedin three rows and three columns. The pairs of slopes 15 s and the pairsof slopes 15 t face the openings of the light-emission spaces 17.

Each light-reflecting member 15 has a light-reflecting property, sothat, with the slopes 15 s and 15 t of the wall portions 15 ax and 15ay, light emitted from the light-emitting elements 21 is reflectedtoward the opening of the light-emission space 17. Moreover, lightincident on the bottom portion 15 b is also reflected toward the openingof the light-emission space 17. Accordingly, light emitted from thelight-emitting elements 21 can be efficiently incident on thelight-transmissive layered structure 50.

Each of the light-emission spaces 17 demarcated by the light-reflectingmembers 15 serves as the smallest unit of light-emission space when theplurality of light-emitting elements 21 are driven separately. Each ofthe light-emission spaces 17 also serves as a smallest unit region forlocal-dimming when the light-emitting module 101, as a surface emissionsource, is viewed from the upper surface of the light-transmissivelayered structure 50. With this structure, a light-emitting module inwhich local-dimming driving can be performed with respect to thesmallest units of light-emission spaces, when the plurality oflight-emitting elements 21 are driven separately. By simultaneouslydriving adjacent ones of light-emitting elements 21 to synchronize thetiming of turning ON and OFF, local-dimming driving based on largerunits of light-emission spaces is also possible.

The light-reflecting members 15 may be obtained by, for example, moldinga resin that contains a reflective material composed of metal oxideparticles such as titanium oxide, aluminum oxide, or silicon oxide;alternatively, the light-reflecting members 15 may be obtained bymolding a resin that does not contain any reflective material, anddisposing a reflective material. It is preferable that, the reflectanceof each light-reflecting member 15 with respect to light emitted fromthe light-emitting element 21 is, for example, 70% or more.

The light-reflecting members 15 can be formed by a molding method usinga mold or by stereolithography. Examples of molding methods using a moldinclude injection molding, extrusion molding, compression molding,vacuum forming, pneumatic forming, press forming, and the like. Forexample, through vacuum forming using a reflection sheet that is made ofPET or the like, light-reflecting members 15 can be obtained in each ofwhich the bottom portion 15 b and the wall portions 15 ax and 15 ay areintegrally formed. The thickness of the reflection sheet may be, forexample, in a range of 100 μm to 500 μm.

The lower surface of the bottoms 15 b of the light-reflecting members 15and the upper surface of the insulating layer 13 are fixed together byan adhesion member or the like. The insulating layer 13 that is exposedthrough the through-holes 15 e preferably has a light-reflectiveproperty. it is preferable that an adhesion member is disposedsurrounding of the through-holes 15 e so that light emitted from thelight-emitting elements 21 is not incident at a portion between theinsulating layer 13 and the light-reflecting members 15. For example, anadhesion member may be disposed in an annular shape along the outer edgeof each through-hole 15 e. The adhesion member may be a double-sidedtape, a hotmelt-type adhesive sheet, or an adhesive liquid of athermosetting resin or a thermoplastic resin. It is preferable that suchadhesion members are highly incombustible. Instead of an adhesionmember, screws, pins, or other means of coupling may be used for fixing.

Each region Ru surrounded by a light-reflecting member 15 can beregarded as a single light-emitting module 101 including alight-emitting element 21. In other words, the integrated light-emittingdevice 103 includes a plurality of light-emitting modules 101 that arearranged along the x direction and the y direction with an intervalP_(x) and an interval P_(y).

The height H_(R) of each light-reflecting member 15 is preferably equalto or less than 0.3 times, and more preferably equal to or less than 0.2times, of the arrangement interval of the light-emitting modules 101. Inthe case in which the light-emitting modules 101 are arranged in atwo-dimensional array, “the arrangement interval” as used herein refersto the shorter one of the intervals along the two directions. In thepresent embodiment, the arrangement interval P_(x) along the x directionand the arrangement interval P_(y) along the y direction are equal, andthus the height H_(R) is equal to or less than 0.3 times the P_(x) orP_(y), i.e., H_(R)≤0.3P_(x) or H_(R)≤0.3P_(y). With the height H_(R) ofeach light-reflecting member 15 that satisfies this condition, thedistance between the light-transmissive layered structure 50 and theintegrated light-emitting device 103 can be reduced, so that thin-typelight-emitting modules can be obtained.

The light-transmissive layered structure 50 includes the half mirror 51.The structure of the light-transmissive layered structure 50 is as hasbeen described in the first embodiment.

With the integrated light-emitting module 102, as in the firstembodiment, unevenness in luminance can be reduced even with a thin-typestructure.

A light-emitting module and integrated light-emitting module accordingto the present disclosure can be used for various light sources, such asbacklight devices for liquid crystal display devices and illuminationdevices.

The above disclosed subject matter should be considered illustrative,and not restrictive, and the appended claims are intended to cover allmodifications, enhancements, and other embodiments that fall within thetrue spirit and scope of the present disclosure. Thus, to the maximumextent allowed by law, the scope of the present disclosure may bedetermined by the broadest permissible interpretation of the followingclaims and their equivalents, and shall not be restricted or limited bythe foregoing detailed description.

What is claimed is:
 1. A light-emitting module comprising: a base bodycomprising electrical conductor wirings; a light-emitting elementdisposed on the base body and electrically connected to the electricalconductor wirings; a light reflection film disposed on an upper surfaceof the light-emitting element; and a half mirror disposed on a lightextraction surface side of the light-emitting element and spaced apartfrom the light-emitting element; wherein a spectral reflectance of thehalf mirror under perpendicular incidence at a wavelength longer than apeak emission wavelength of light emitted from the light-emittingelement is greater than a spectral reflectance of the half mirror underperpendicular incidence at the peak emission wavelength, and wherein:when an emittion peak wavelength region is defined as a wavelengthregion with a predetermined width including a peak emission wavelengthat a center thereof; and a spectral reflectance of the half mirror underperpendicular incidence in a wavelength region located 50 nm from theemission peak wavelength region on a longer wavelength side of thelight-emitting element is 10% or more greater than a spectralreflectance of the half mirror under perpendicular incidence in theemission peak wavelength region of the light-emitting element.
 2. Thelight-emitting module of claim 1, wherein a spectral reflectance of thehalf mirror under perpendicular incidence in the emission peakwavelength region of the light-emitting element is in a range of 30% to65%.
 3. The light-emitting module of claim 1, further comprising: asealing member covering the light-emitting element and the lightreflection film; wherein a ratio H/W of a height H to a width W of thesealing member is smaller than 0.5.
 4. The light-emitting module ofclaim 3, wherein the ratio H/W is 0.3 or smaller.
 5. The light-emittingmodule of claim 1, wherein a reflection wavelength band of the lightreflection film under perpendicular incidence includes a peak emissionwavelength of the light-emitting element, and is wider on a longerwavelength side of the emission peak wavelength than on a shorterwavelength side.
 6. The light-emitting module of claim 1, wherein 30% ormore of a total amount of light emitted from the light-emitting elementis emitted at an angle of elevation less than 20° with respect to theupper surface of the base body.
 7. The light-emitting module of claim 1,wherein 40% or more of a total amount of light emitted from thelight-emitting element is emitted at an angle of elevation that is lessthan 20° with respect to the upper surface of the base body.
 8. Thelight-emitting module of claim 1, wherein the light-emitting element isflip-chip mounted on the base body.
 9. The light-emitting module ofclaim 1, further comprising a wavelength conversion member disposed onthe light extraction surface side of the light-emitting element, thewavelength conversion member being adapted to absorb a portion of lightemitted from the light-emitting element and to emit light of awavelength different from an emission wavelength of the light-emittingelement.
 10. An integrated light-emitting module comprising: a pluralityof the light-emitting modules of claim 1; and a plurality oflight-reflecting members, each disposed between an adjacent two of theplurality of light-emitting modules.
 11. The integrated light-emittingmodule of claim 10, wherein a height of each light-reflecting member isequal to or less than 0.3 times a distance between the light-emittingmodules.
 12. The integrated light-emitting module of claim 10, wherein aheight of each light-reflecting member is equal to or less than 0.2times a distance between the light-emitting modules.